1. Technical Field
This invention relates to substrate processing chambers and, in particular, to door assemblies for controlling the formation of deposits within tunnels of the door assemblies.
2. Description of the Related Art
Wafer etching processes performed within conventional processing chambers often result in the accumulation of etch byproducts on walls of the processing chambers, as well as on other exposed components. Accumulated byproducts can impair processing quality and can reduce overall processing efficiency, thereby leading to reduced throughput. For example, solid polymer byproducts often form deposits at the tops of door tunnels. These deposits tend to peel and form flakes. Additional polymer byproduct may be deposited on the flakes and cause additional peeling that ultimately results in large hanging formations commonly referred to as “stringers.” Stringers may obstruct door tunnels and may scratch the top surfaces of wafers. These types of scratches may result in a significant yield loss, for example, about a 5% yield loss per each scratched wafer. FIG. 1 shows a stringer 50 hanging downwardly into a door tunnel 54. If the stringer 50 is not removed, it may continue to peel away to further reduce the amount of clearance in the door tunnel 54. It may be difficult to load and unload the chamber without damaging wafers, especially if more than one stringer forms along the tunnel 54.
Fabrication processes, such as metal etching, tend to produce significant amounts of byproducts that lead to the formation of stringers. For example, stringers often form in the door tunnels of plasma etching chambers. Processing gases are contained in plasma etching chambers, while radio frequency (RF) power is used to ignite the processing gases. The ignited processing gases form plasma that etches a targeted layer (e.g., a metal layer) of the wafer. These etching processes often result in etch byproducts that produce relatively large stringers within about a few hundred RF hours. Door tunnels of plasma etching chambers are frequently cleaned to remove these stringers. In some conventional metal etchers, stringers that extend downwardly a distance D (see FIG. 1) greater than or equal to about 3 cm may be produced in less than about 500 RF hours.
Leaks can contribute to stringer growth. When a door assembly leaks (for example, leaks between a door and a front face of a chamber), gases flow through the door tunnel towards the leak. Etch byproducts are drawn into and accumulate within the door tunnel. If the leak is detected, it may be difficult to reposition the door to eliminate the leak. Conventional doors may be aligned with the front face of the chamber with a high level of accuracy to maintain a sealed chamber. Unfortunately, it is difficult to open and close door assemblies repeatedly with the required high level of accuracy.
After deposits build up in the processing chambers, cleaning operations, such as dry cleaning operations or wet cleaning operations, are performed. Dry cleaning operations are often unsuitable for removing large buildups, such as stringers in the door tunnels. Wet cleaning operations are performed by opening processing chambers and wiping down interior surfaces of the chambers. Wet cleaning operations result in significant down-time and, thus, reduce processing throughput.